（§是因为的意思,#是所以的意思）(1)§Gc=800N,F压=p1S=300Pa*1m^2=300N,#杠杆B端对配重C的拉力FB=Gc-F压=800N-300N=500N.§FB*OB=FA*OA,#工作台和卷扬机对杠杆A端的压力FA=FB*(OB/OA)=500N*(5/2)=1250N.由图可知,拉力F1的功率P1=W/t=900J/2s=450W.§绳端速度v1'=nv1=3*0.2m/s=0.6m/s,#拉力F1=P1/v1'=450W/(0.6m/s)=750N.#工作台和卷扬机的重力G=FA-F1=1250N-750N=500N.(2)§F压'=p2S=200Pa*1m^2=200N,#杠杆B端对配重C的拉力FB'=Gc-F压'=800N-200N=600N.§FB'*OB=FA'*OA,#工作台和卷扬机对杠杆A端的压力FA'=FB'*(OB/OA)=600N*(5/2)=1500N.#拉力F2=FA'-G=1500N-500N=1000N.§v1:v2=2:3,#v2=0.3m/s.#绳端速度v2'=nv2=3*0.3m/s=0.9m/s.#拉力F2的功率P2=F2v2'=1000N*0.9m/s=900W.(3)§F1=(1/n)(G1+G动),F2=(1/n)(G2+G动),#G1=G2+nF1-nF2=2750N+3*750N-3*1000N=2000N.#伊塔1=W有用/W总=G1h/(F1nh)=G1/(nF1)=2000N/(3*750N)=8/9,伊塔2=W有用'/W总'=G2h/(F2nh)=G2/(nF2)=2750N/(3*1000N)=11/12.#伊塔1:伊塔2=8/9/(11/12)=32:33.